Thermoplastic polyester resins can have good chemical resistance, mechanical strength, and electrical insulatability, among other properties, and have accordingly been widely used in the production of electric/electronic parts, housings of automobile parts, connectors and the like.
In the field of electric and electronic devices, flame retardancy is especially required to ensure stability during a fire. A widely known method for imparting flame retardancy is the addition of a halogen-containing compound with an antimony oxide and metal oxide as a flame-retardant aid. However, such methods are disadvantageous because halogen gases released by thermal decomposition during molding processes can corrode the mold. Further, such toxic gases are undesirable in the workplace.
In particular, halogenated dioxin generated during a fire or combustion is harmful to humans and may cause environmental contamination. Accordingly, the use of halogen-containing flame retardant s has recently been restricted by law under TCO (The Swedish Confederation of Professional Employees). Thus, currently efforts are ongoing worldwide to develop technologies using halogen-free flame retardants as a substitute for halogen-containing flame retardants.
Japanese patent application laid-open No. 10-195283 discloses a polybutylene terephthalate resin composition using a phosphoric acid ester as a flame retardant. However, in this case, a large amount of flame retardant is needed to obtain sufficient flame retardancy. As a result, production costs may increase and the mechanical properties of the resin composition can be deteriorated.
U.S. Pat. No. 6,569,928 discloses a polyester resin composition comprising a melamine compound (melamine cyanurate) and phosphoric acid ester. However, this composition also requires a large amount of flame retardant to obtain flame retardancy, which results in deterioration of moldability and mechanical properties.